The invention relates to a suction device to draw off liquid from filtration vessels to recipient vessels according to the preamble of claim 1.
It is known to separate, add, analyze etc. sample liquids or components thereof by introducing them into filtration vessels and drawing off filtered matter into recipient vessels disposed below them. The filtration vessels have a charging seat with an upper opening to fill in sample liquid, a lower outlet opening for the filtered matter, and a filter associated with it. They may be made of polypropylene, polystyrene or another appropriate material and have a charging capacity of about 10 ml to about 200 xcexcl or less. The filtering materials used are, for example, porous membranes and/or silica and/or diatomaceous earth. Filtration vessels may particularly be individual filtration vessels, arrays of individual filtration vessels, strip-type filtration vessels, arrays of strip-type filtration vessels or microtitration filter plates (also referred to as xe2x80x9cmembrane-type microtitration platesxe2x80x9d), the latter comprising a multiplicity of recipent vessels in a matrix arrangement which corresponds to the matrix arrangement of a membrane-type microtitration plate.
To draw the sample liquid off, at least one filtration vessel is mounted in a marginally sealing way on a suction device so that its outlet opening faces an evacuable chamber of the suction device. At least one recipient vessel is disposed in the chamber below the at least one filtration vessel, which receives the sample liquid trickling down from the filtration vessel. An individual filtration vessel, an array of individual filtration vessels, a strip-type filtration vessel or an array of strip-type filtration vessels may be disposed in a perforated plate or another mounting and may be disposed across them in a marginally sealing way on a suction device. Accordingly, the various designs of the recipient vessels may be disposed in a mounting.
A suction device of the type mentioned at the beginning including an evacuable chamber which has an upper opening with a continuous circular sealing surface which approximately extends horizontally for marginally supporting a membrane-type microtitration plate mountable in place from top and may be opened for the insertion and removal of a microtitration plate recipient vessel, and including a support to enable the microtitration plate recipient vessel to be positioned in the chamber below the membrane-type microtitration plate and in parallel thereto is known from DE 41 07 262 C2. To improve the handling properties and to reduce the hazard of contamination, the support of the microtitration plate recipient vessel is disposed on a carrier which is adapted to be displaced, through a feed opening of the chamber, up to a charging position in the chamber, in which the microtitration plate recipient vessel will then be disposed below the membrane-type microtitration plate, the carrier is connected to a front plate which sealingly bears on the edge of the feed opening in a charging position, and the carrier is adapted to be displaced from the chamber, through the feed opening, into an access position for the insertion and removal of the microtitration plate recipient vessel.
In this suction device, the membrane-type microtitration plate and the microtitration plate recipient vessel are positioned and removed manually. While the microtitration plate recipient vessel is being displaced by means of the drawer-like carrier accelerations and concussions may occur by which sample liquid may drop down from the membrane-type microtitration plate or flow over from recipient vessels. This can lead to liquid losses and contaminations of the recipient vessels and the chamber. Already for this mere reason, an automation of the charging and discharging operations for the suction device would pose a problem.
The filtration vessels and recipient vessels require to be aligned to each other as precisely as possible in the suction device. Errors of alignment, pull-off effects, and aerosol formation may also cause losses and contaminations during the transfer of filtered matter from filtration vessels to recipient vessels. Also, for an optimum transfer of filtered matter, filtration vessels of a special drop-down contour which are centrally aligned to the matching recipient vessel have already been proposed.
DE 41 27 276 C2 discloses a sample liquid separation device wherein a filtration vessel has moulded to it an outlet tube joining an outlet opening and a socket surrounding the tube, on which a recipient vessel is adapted to be attached such that an exchange of air is possible between the interior of the recipient vessel and its surroundings. The outlet tube protrudes beyond the socket into the recipient vessel so that a drop which is at the end of the outlet tube does not get into the area of contact of the filtration vessel and recipient vessel. It is true that a loss of liquid and contamination are largely avoided by the device. However, the arrangement of the filtration vessel and recipient vessel with regard to each other and to a suction chamber is an expenditure and is carried out manually.
Accordingly, it is an object of the invention to create a suction device which favours low-loss and low-contamination operation and automation thereof.
The object is attained by a suction device having the features of claim 1, further by a suction device having the features and, finally, by a suction device having the features. Advantageous aspects of the suction devices are indicated in the sub-claims.
The first solution variant is characterized in that the upper opening having the continuous circular sealing surface is disposed on a first chamber portion which is adapted to be displaced with regard to a stationarily disposed, second chamber portion having a support, the first and second chamber portions complementing each other to form a sealed chamber in a charging position and the first chamber portion releases the support for the insertion and removal of the at least one recipient vessel in an access position displaced away from the second chamber portion. The first chamber portion may be adapted to be displaced here, particularly in parallel with or perpendicularly to the support.
The fact that the second chamber portion having the support is disposed stationarily prevents a recipient vessel positioned on the support from being moved while the first chamber portion is being displaced, which avoids liquid losses and contaminations. For the same reason, it is possible to position the filtration vessel on the first chamber portion only after the latter is displaced into the charging position and to remove the vessel from the first chamber portion before the latter is displaced into the access position. In addition, auxiliary means associated with the stationary support may be realized at a lower expenditure. Altogether, this will also favour the automation of suction device operation.
The second solution variant is characterized in that the chamber has at least one lateral opening including a closure, which releases the opening into an access position for the insertion and/or removal of at least one recipient vessel and sealingly closes the opening in a charging position, and that the recipient vessel is adapted to be displaced from an access position disposed outside the chamber, through the opening, into a charging position below the position of the filtration vessel, and vice versa. The displacement of the recipient vessel may preferably be effected along a guide.
Since the recipient vessels are of a relatively small weight accelerations and concussions which can lead to mixing and the loss of liquid may be avoided during the insertion and removal of the recipient vessels, which may be performed without any concurrent displacement of further device components. Moreover, the mere displacement of the recipient vessels will favour the rapid succession of suction operations and the easy design of auxiliary means. Altogether, this will favour automation as well.
The third solution variant is characterized in that the support is adapted to be vertically displaced towards the upper opening by means of a lifting device within the chamber to dispose the recipient vessel close to the filtration vessel in a charging position.
The approach of the recipient vessel to the filtration vessel, which can be effected until the recipient vessel is moved in part onto the filtration vessel, serves to avoid losses and contaminations when the filtered matter flows out. By means of the lifting device, a displacement within the closed chamber may be caused, which helps avoid an expenditure in manual positioning. The lifting device is an auxiliary means acting on the recipient vessel so that the third solution variant can be realized in a particularly advantageous way along with the first solution variant or the second solution variant. Even this solution variant will favour an automation of suction device operation.